Strengthening of reinforced concrete beams in shear by the use of externally bonded steel plates: Part 1 – Experimental programme

This paper describes a programme of research to investigate the behaviour of reinforced concrete beams strengthened in shear by means of externally bonded steel plates and hence to provide engineers with appropriate design guidance. The shear strengthening and testing to failure of 15 rectangular section reinforced concrete beams was conducted. To account for the different potential types of shear failure (diagonal tension, shear compression and deep beam failure) three shear span to depth ratios were used. A further 15 experiments were then conducted using ‘T’section beams. In most cases the addition of externally bonded shear plate reinforcement provided enhancement in shear capacity comparable with that provided by conventional internal shear links designed to BS8110 [British Standards Institute (BSI). Structural use of concrete, Part 1: Code of practice for design and construction. BS 8110: Part 1: BSI. London; 1997]. Measurement of the principal strains in the plated beams showed that as well as tensile and compressive strains due to bending, strains arising from an underlying shear crack are evident. Hence the plates serve to control crack opening and catastrophic shear failure up to a certain load level, when bond failure occurs in the concrete. The use of partial depth plates with T section beams does not appear to be as successful as the use of full depth plates on rectangular section beams.